1. Field of the Invention
The invention relates to a printing machine with printing groups or printing group parts driven by at least one electric motor.
2. Discussion of the Prior Art
In the simplest case, printing machines are driven by a single motor that drives a mechanical longitudinal shaft. In more advanced designs, the longitudinal shaft is broken up, and the resulting parts are driven by individual angle-controlled motors that operate in angle-synchronicity. In further configurations, printing units or even parts of printing groups, such as form cylinders or transfer cylinders, are driven by individual associated angle-controlled motors.
For example, a rotary offset printing machine with directly driven cylinders is known from the article "Direktantriebstechnik" ["Direct Drive Technology"] by F. R. Goetz in Antriebstechnik [Drive Technology] 33 (1994) No. 4, pp. 48 to 53. Printing machines of this type, driven by multiple motors in accordance with the individual drive principle, have a simpler mechanical structure than printing machines with a longitudinal shaft. Intermediate gearwheels and couplings between the individual printing groups or printing group units are omitted, as are circumferential register adjustments. The use of water-cooled motors of small structural size and optimal heat control allows the structure of such printing machines to be further improved. Because the components of the printing machine are mechanically disconnected, they cannot vibrate against each other. Moreover, the "virtual" coupling of printing groups to one another entails no additional mechanical expense. Particularly in printing machines for printing on webs, a large number of web guides can be realized simply.
All printing machines driven by electric motors experience periodic and non-periodic disturbances. The load torque reacting on an electric motor of the printing machine or the printing machine part (i.e., a cylinder, cylinder pair or group of cylinders or rollers) driven by that motor represents a disturbance variable in the control loop. Disturbances that occur periodically, e.g., the impacts in the inking mechanism of a vibrator, which executes a pendulum movement between an ink duct and an ink transfer roller, pose particular problems. Other periodic disturbances result, for example, from the cross-wise cutting of the printing web, from the movement of a folding blade in a knife folding mechanism that produces a third fold, from the channel impact associated with clamping channels in form and transfer cylinders, and from non-circularities in paper and transport rollers.